The present invention is directed to a strapping machine. More particularly, the present invention pertains to a self-adjusting stripper pin for a strapping machine strap chute to eject strap from the strap chute track.
Strapping machines are in widespread use for securing straps around loads. One type of known strapper includes a strapping head and drive mechanism mounted within a frame. A chute is mounted to the frame.
During the strapping operation, strapping material is fed from the strapping head, through the strap chute and back around to the strapping head. The strap is withdrawn from the strap chute (or chute track) and tensioned. The strap, at overlying courses, is sealed onto itself to form a strap joint. Such strapping machines and their construction and operation are disclosed in Bobren, et al., U.S. Pat. No. 7,395,754, Holden, et al., U.S. Pat. No. 7,263,928, Bobren, et al., U.S. Pat. No. 6,962,109, Lininger et al., U.S. Pat. No. 6,951,170 and Bobren, U.S. Pat. No. 6,910,318.
The strap chute is formed by inner and outer races or track walls with a gap between the races. The gap defines the chute track. The strap traverses from the strapping head, through track (the gap between the races) and back to the head.
When the strap returns to the strapping head, it is stripped from the track, tensioned, and sealed. In order to strip the strap, a stripping pin is inserted into the track, transverse to the direction of strap travel, to strip or push the strap out of the track.
Known stripper pins are one-piece pins that are fixed in place. The back side of the pin is held against a rigid surface and the opposing side of the pin is held in place by a compression spring. In the closed chute position, the tip of the pin remains partially in the track but out of the path of the strap. When the chute is opened (in a position such that the strap is pushed or urged out of the track), the chutes slides (with the pin fixed) and the tip of the pin pushes the strap out of the track.
When the chute is open, the pin must be about flush to about one (1) millimeter beyond the track wall edge. If the pin extends too far when the chute is open, the strap can get caught on (snagged on) the pin, which can cause a “pre-seal”, which is a seal with the strap still in the chute. If the pin fails to fully eject the strap from the track, this can also result in a pre-seal.
In order to overcome the over and under pin travel problems, field changes or corrections are made in which the bracket to which the pin is secured (at the fixed back end) is bent toward or away from the chute to provide optimum pin setting. Although this fix works, it is not the most efficient manner in which to provide proper pin setting. Moreover, if maintenance is performed on the strapping machine (for example, at the chute), the field adjustment (bending of the chute) may have to be performed again to properly re-set the pin setting.
Accordingly, there is a need for a self-adjusting stripper pin to improve strap ejection from a strapping machine. Desirably such a pin can be used in place of existing fixed stripper pins. More desirably, such a stripper pin is self-aligning and self limiting relative to the chute track. More desirably still, such a stripper pin is biased to provide tolerance in movement.